This invention relates in general to mining devices and in particular to a new and useful railess vehicle for use underground.
In many mining operations underground, the use of Diesel vehicles is very problematic, due to the ventilation conditions. Loading of the mine air with waste heat and noxious substances from a Diesel engine cannot always be compensated for, and at least the ventilating costs are considerably increased if Diesel vehicles are employed. For this reason, electrically operated, railess vehicles are used at a growing rate, with which these air loading factors are absent or at least minimized. Since underground loaders and hauling vehicles must handle large amounts of material within short periods of time, even with a simultaneous negotiation of slopes, their drives must be correspondingly strongly dimensioned. With a plurality of power inputs for separate drive mechanisms on the vehicle, this leads to designs of mine vehicles which are clumsy in the restricted space conditions underground.
The power for the vehicle is supplied through a line leading from stationary underground energy sources to the vehicle, where it is wound onto a magazine drum. Now, depending on the travel direction of the vehicle, the power supply line must be either wound up or unwound from the drum. The direction of rotation and angular speed of the magazine drum are derived from the respective tensile stress in the supply line. A constant, more or less high and swelling tensile stress in the supply line, frequently leading to whipping movements, wears the line down rapidly and damages it mechanically to a large extent.
Therefore, in cable drums equipped with a separate drive motor, it has already been provided to determine the variations in the slack of the freely extending portion of the supply cable by means of a sensing device, and transmit them to an electric or switching device (German Pat. No. 55696). This is accomplished by means of a pendulum-type twing arm bearing against the supply cable through rollers. Further, the elimination of the tensile stress is particularly dealt with in German OS No. 23 37 425. In both instances, the control signals effect a variation in the speed of the drum driving motors. Such speed-controlled electric motors (stop motors) are subject to particularly strong loads when the are started with a full rated torque from their standstill position. Such drive motors require much power and must be bulky and heavy to satisfy the requirements imposed on them in underground service. Under the conditions of higherpower and dynamic reversing operations underground, partly with the supply line fully wound up on the magazine drum, such motors are uneconomical. The electrical drive disclosed in the abovementioned German OS No. 23 37 425 is yet bulkier, due to a provided drive motor, and is burdened with high power losses, particularly upon an application of the maximum torque while starting the drum.